The Charles River is a form of Jungle Juice that is made of roughly a half of bottle of Everclear, a half litter of Tequila, roughly 6 cans of light beer, a mixture of pink lemonade and yellow lemonade and some packets of sugar. It looks extremely nasty but it gets the job done. Also if you throw a condom in the mix it will look like The Charles River in Boston.

Guy1: Dude, that Jungle Juice looks like the fucking Charles River
Guy 2: Dude, it IS the Charles River; it'll get you fucked up.